Electro-optic rearview mirrors are well known in the art for example, in U.S. Pat. Nos. 5,140,455 and 5,151,816 and as described in the following paper: N. R. Lynam "Electrochromic Automative Day/Night Mirrors" SAE Technical paper series (870636) (1987).
Prismatic type rearview mirrors are also well known in the art.